This investigation addresses itself to the problem of fixation in total joint replacement by the development and application of a porous fiber metal composite to obtain fixation to bone by bone ingrowth; the evaluation of wear in the articulating surfaces of artificial joints; the evaluation of the related biocompatibility problems. Studies include: a.) A continuing study of the carcinogenesis of fiber metal composites in a rat model, b.) A canine total hip replacement and a canine total hip surface replacement has been developed and is under evaluation. Success in all animals has been encountered in the fixation of the femoral component. Problems have developed in the acetabular components but these are primarily secondary to the technical design of the prosthetic design. c.) A study of ingrowth in a steroid-induced osteoporosis model is under progress. d.) Studies are also in progress in the determination of the magnitude of metal ion release from the fiber metal composite and the potential adverse biological effects. These studies include evaluation of titanium in porous form and cobalt-chrome alloy in porous form. e.) A program of evaluation of wear in UHMW PE is also in progress. Studies are centered, in present, on the wear of titanium as a function of the characteristics of the passivation layer induced by a different number of treatments. Other studies center on the relation between crystallinity of UHMW PE and wear.